摘要
自 2 0世纪 30年代以来 ,美国的土壤保护大致经历了两个阶段 ,即 30年代到 6 0年代注重减轻土壤侵蚀 ,增加农田生产力的土壤保护和 70年代到 90年代注重减轻土壤侵蚀对环境影响的土壤保护 .6 0年来 ,经过大量治理项目的实施 ,土壤侵蚀得到了有效的控制 。
The land conservation in the United States has been undergoing two periods since 1930's.One is from 1930's to 1960's when reducing soil erosion for increasing the production of fields was emphasized,the other is from 1970's to 1990's when the effect of soil erosion on environment was highly thought.For the past 60 years,soil erosion has been controlled effectively by carrying out a number of programs.
出处
《许昌师专学报》
2000年第2期93-95,共3页
Journal of Xuchang Teachers College(Social Science Edition)
